Recently, automatic machines for packaging electronic parts have been developed. For example, when electronic parts are to be adhesively fixed to a printed circuit board, an automatic adhesive applying machine, such as one disclosed in Japanese Laid-open Patent Application 3-217100, is used as an apparatus for applying an adhesive to the fixing positions, wherein the amount of adhesive applied is automatically detected and on the basis of the result of the detection the amount of adhesive to be subsequently applied is corrected, whereupon the adhesive is automatically applied to the printed circuit board.
The conventional adhesive applying method using the aforesaid automatic adhesive applying machine will now be described with reference to FIGS. 4 and 5. In addition, the production program which sets the conditions for applying adhesive is composed of some blocks of data on the conditions for production, and the production program is headed with data on the conditions for correction used to correct the applying time. The data on the conditions for correction determines the time required for adhesive application and the prescribed amount of adhesive to be applied then.
FIG. 4 is a partial perspective view of an automatic adhesive applying machine for carrying out the conventional adhesive applying method, illustrating a head section for applying an adhesive, an actuating section for moving the head section to adhesive applying positions, and a detecting section for detecting the amount applied.
In FIG. 4, the head section comprises a mechanism section 402 supporting some tanks 401 which hold an adhesive and adapted to vertically and independently move one of the tanks 401 which is selected by the production program when performing an adhesive applying operation, an air control section 403 for pneumatically forcing a predetermined amount of adhesive out of the tank 401 which is independently moving up and down, and a recognition camera 404 for detecting the amount of adhesive applied. Further, each tank 401 comprises a nozzle or nozzles 405 through which the adhesive is forced out, and a plug 406 for confining the adhesive.
The actuating section comprises an X-axis robot 407 which longitudinally moves said head section, and a Y-axis robot 409 which transversely moves a table 408.
The detecting section comprises a tape 410 used for trial adhesive application in order to correct the amount of adhesive applied, a detecting table 411 for assisting in the application of adhesive onto the tape 410, and a cartridge 412 for holding the tape 410.
In the thus-constructed automatic adhesive applying machine, the adhesive applying operation is an operation for applying a predetermined amount of adhesive to predetermined positions on a board 413 held on the table 408, said operation comprising the steps of effecting positioning by means of the X-and Y-axis robots 407 and 409 according to positional information contained in the production program, forcing the adhesive in one or more tanks 401, selected by the production program, by an amount prescribed by the production program, to the tips of the nozzles 405, by pushing the associated plugs 406 by the air control section 403, and moving them up and down to apply the predetermined amount of adhesive to predetermined positions on the board 413.
Further, the adhesive application correcting operation is an operation for applying the adhesive for a predetermined time which is set by the data on the conditions for correction prior to performing a productive adhesive applying operation, so as to confirm whether or not the prescribed amount of adhesive has been applied, and if the prescribed amount of adhesive has not been applied, the applying time is adjusted to ensure that the prescribed amount of adhesive is applied.
In this adhesive application correcting operation, first the adhesive is applied to predetermined positions on the tape 410 supported on the table 411 and the amount of thus-applied adhesive is detected by the recognition camera 404. The amount of adhesive detected is compared with the prescribed amount of adhesive set by the data on the conditions for correction, and the applying time is adjusted to perform an adhesive application correcting operation again.
When the amount of adhesive applied for the applying time adjusted last time by the adhesive application correcting operation has finally converged to the prescribe amount of adhesive set by the data on the conditions for correction, the adhesive application correcting operation is terminated and is taken over by the productive adhesive applying operation. In this case, when the adhesive applying operation has been performed by a predetermined number of times, the tape 410 is fed out a predetermined length so as to prevent coatings of adhesive applied from overlapping each other. A series of adhesive application correcting operations are thus completed.
Referring to the adhesive application correcting method in the conventional adhesive applying method, the operation will now be described with reference to FIG. 4 by using a flowchart as shown in FIG. 5. In addition, in this adhesive application correcting method, the production program has been drafted so that an adhesive application correcting operation will be performed prior to a productive adhesive applying operation on a board.
First, at step #51, one of the tanks 401 is moved to the position of the detecting table 411 which is set by the data on the conditions for correction in the production program and a corrective adhesive applying operation is performed, in which the adhesive is discharged for a predetermined time which is set by the data on the conditions for correction. At step #52, the recognition camera 404 is moved to the detecting table 411 to detect the amount of adhesive.
At step #53, a decision is made as to whether the amount of adhesive detected at the step #52 is within the range of the allowable limits of the prescribed amount set by the data on the conditions for correction. If the amount of adhesive is not within the range of allowable limits, at step #52 the applying time is adjusted to correct the amount of adhesive to be applied. That is, if the amount of adhesive is too much, the corrected amount is such as to shorten the applying time, while if it is too small, the corrected value is such as to prolong the applying time. After the adjustment of the applying time, the program returns to step #51 and the adhesive application correcting operation is repeated.
On the other hand, if the decision made at step #53 is within the range of the allowable limits of-the prescribed amount set by the data on the conditions for correction, the program moves to step #55, where the corrected value of the applying time obtained by said adhesive application correcting operation is used to adjust the applying time in the data on the conditions for production in the production program and a productive adhesive applying operation is performed.
At step #56, the productive adhesive applying operation is interrupted and a decision is made as to whether to perform an adhesive application correcting operation. If an adhesive application correcting operation is not to be per formed, the program moves to step #55 and the productive operation is continued. If an adhesive application correcting operation is to be performed, the program moves to step #51 to perform such corrective operation so as to find a corrected value again.
In the case of a continuous productive adhesive applying operation, such operation may be continued until the adhesive in the tanks is used up. When the absence of adhesive in the tanks has been detected, the production is interrupted and a warning lamp or the like is used to notify the operator of the operation being interrupted.
Recently, in the field of packaging of parts, the frequency of the use of an adhesive during production has increased owing to packaged parts being in chip form or owing to the use of a large-sized board, such as a mother board in a computer, for packaging parts thereon. As a result, there has been a need for an automatic adhesive applying machine corresponding to an adhesive applying method which is capable of accurately effecting more stabilized application of adhesive.
With the aforesaid conventional adhesive applying method, however, in order to achieve stabilized application of a given amount of adhesive at all times in a continuous productive adhesive applying operation, it is necessary to change the conditions for adhesive application, i.e., the applying time, air pressure for adhesive application, etc., according to the amount of adhesive in the tanks, it being difficult to realize a stabilized continuous adhesive applying operation for applying a fixed amount of adhesive all the times.
As an approach to this problem, there is an adhesive application correcting method which adjusts conditions for applying a predetermined amount of adhesive each time the production of a given number of boards is completed. With such adhesive application correcting method, however, there arises a new problem that changes in the amount of adhesive applied during the production of a given number of boards cannot be corrected.
Further, another problem is the interruption of production owing to a shortage of adhesive during the adhesive applying operation. Other problems are that since said shortage of adhesive occurs suddenly, it takes substantial time to prepare a new supply of adhesive to resume production, and that such interruption of productive adhesive applying operation detracts from the reliability of boards produced.